1. Field of the Invention
The present invention relates to a microwave oven with a structure for guiding electromagnetic wave. More particularly, the present invention relates to a microwave oven with a structure for guiding electromagnetic wave in which a microwave generated by a magnetron is dispersed with a maximum electromagnetic field intensity.
2. Prior Art
Generally, a microwave oven is a device for cooking material or foodstuff by microwave. The microwave oven is provided with an electric device chamber with a magnetron for generating microwave and a heater for generating heat. A high voltage is generated by mutual inductance of the first and second coils of a high voltage transformer, and the high voltage is applied to the magnetron to generate microwave. The microwave is irradiated to a cooking chamber through a waveguide in the microwave oven. The irradiated microwave inside the cooking chamber heats and cooks the material or foodstuff.
The conventional microwave oven will be described in detail with reference to FIG. 1 below.
FIG. 1 is a schematic cross-sectional view for showing a structure of the conventional microwave oven. In FIG. 1, a magnetron 10 generates an electromagnetic wave, and more minutely a microwave, by circuitry of the controlling part. The electromagnetic wave generated from magnetron 10 propagates through the waveguide 20. The electromagnetic wave flows into a cooking chamber 60. The cooking chamber 60 is provided with an opening 30 formed at the border with the waveguide 20, wherein the electromagnetic wave is dispersed into the cooking chamber 60 from the opening 30. A stirring fan 40 is installed in front of the opening 30 inside the cooking chamber 60.
Hereinafter, an operation of the conventional microwave oven will be described.
The electric current with the high voltage is supplied to the magnetron 10, and the microwave, for example about 2,450 MHz, is generated to be irradiated to the waveguide 20. The irradiated microwave propagates through the waveguide 20 to the opening 30. The microwave is dispersed into the cooking chamber 60 from the opening 30. The stirring fan 40 installed in front of the opening 30 is rotated, and thereby the microwave is dispersed effectively inside the cooking chamber 60.
The microwave dispersed into the cooking chamber directly travels to the foodstuff, or it collides with inside walls of the cooking chamber 60 and is then reflected from them to travel to the foodstuff. The microwave incident on the foodstuff conducts a quick molecular translation of about 2,450 million times per second to molecules constituting the foodstuff, and thereby the foodstuff is heated by the molecular motion.
According to the conventional microwave oven, the electromagnetic wave emitted from the magnetron 100, i.e., microwave, has a beam shape formed with a unidirectional flow. While the microwave proceeds along the waveguide 20, the proceeding direction of the wave changes depending on the direction of the waveguide 20. Thereafter, the wave propagates into the cooking chamber 60.
An internal structure of the cooking chamber 60 generally has a rectangular shape. Since the microwave is dispersed from the opening 30 formed at one end of the waveguide 20, the microwave propagates spherically centering about the opening 30. The electromagnetic field intensity of the microwave is in proportion to a square root of an emitted electric power and in inverse proportion to a propagated distance. Furthermore, the spherical electromagnetic field intensity of the microwave depends on the wavelength of the microwave when the emitted electric power and the propagated distance are constant respectively.
In case of the cooking chamber with the rectangular internal structure, the microwave propagated after being reflected from the corners is sharply decreased in the electromagnetic field intensity than the microwave directly propagated to the central part, and thereby the cooking efficiency largely decreases. Moreover, the electromagnetic field intensity of the microwave reaching each part of the foodstuff is different from one part or another, and thereby the heating intensity for the each part is different from one part or another.
According to the conventional microwave oven, because the internal structure of the cooking chamber is a rectangular shape, the microwave is not effectively dispersed and interference and transmission effects deteriorates. Therefore, the cooking efficiency greatly declines, the cooking time is prolonged, and the cooked condition of food may be poor.